// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef UI_VIEWS_ANIMATION_SCROLL_ANIMATOR_H_
#define UI_VIEWS_ANIMATION_SCROLL_ANIMATOR_H_

#include "base/macros.h"
#include "base/memory/scoped_ptr.h"
#include "ui/gfx/animation/animation_delegate.h"
#include "ui/views/views_export.h"

namespace gfx {
class SlideAnimation;
}

namespace views {

class VIEWS_EXPORT ScrollDelegate {
public:
    // Returns true if the content was actually scrolled, false otherwise.
    virtual bool OnScroll(float dx, float dy) = 0;

protected:
    ~ScrollDelegate() { }
};

class VIEWS_EXPORT ScrollAnimator : public gfx::AnimationDelegate {
public:
    // The ScrollAnimator does not own the delegate. Uses default acceleration.
    explicit ScrollAnimator(ScrollDelegate* delegate);
    ~ScrollAnimator() override;

    // Use this if you would prefer different acceleration than the default.
    void set_acceleration(float acceleration) { acceleration_ = acceleration; }

    void Start(float velocity_x, float velocity_y);
    void Stop();

    bool is_scrolling() const { return !!animation_.get(); }

private:
    // Implementation of gfx::AnimationDelegate.
    void AnimationEnded(const gfx::Animation* animation) override;
    void AnimationProgressed(const gfx::Animation* animation) override;
    void AnimationCanceled(const gfx::Animation* animation) override;

    ScrollDelegate* delegate_;

    float velocity_x_;
    float velocity_y_;
    float last_t_;
    float duration_;
    float acceleration_;

    scoped_ptr<gfx::SlideAnimation> animation_;

    DISALLOW_COPY_AND_ASSIGN(ScrollAnimator);
};

} // namespace views

#endif // UI_VIEWS_ANIMATION_SCROLL_ANIMATOR_H_
